NEW YORK, Jan 20, 2026, 18:51 EST — After-hours
- Shares of Rapt Therapeutics jumped roughly 64% in late trading, closing just shy of the takeover bid
- GSK will pay $58 a share in cash, putting the biotech’s value at roughly $2.2 billion
- Attention now turns to the tender-offer documents, antitrust scrutiny, and the expected timeline for a first-quarter close
Rapt Therapeutics (NASDAQ: RAPT) surged roughly 64% to $57.57 in after-hours trading Tuesday following news that Britain’s GSK will acquire the U.S. biotech.
GSK’s $58-a-share cash bid values the deal at about a 65% premium over Monday’s close. This is the first big move by CEO Luke Miels, who just took charge a few weeks ago. Jefferies analyst Michael Leuchten noted that the food allergy sector “is not a crowded market right now,” as GSK braces for patent losses on its HIV drug dolutegravir. Shares in GSK slipped 1.6% in London trading. 1
The prize is ozureprubart, a long-acting anti-IgE antibody. IgE is the immune antibody that triggers many allergic reactions, and GSK said ozureprubart could be dosed every 12 weeks, compared to injections every two to four weeks with current anti-IgE treatments. “Ozureprubart offers the opportunity to bring sustained protection to patients with dosing every 12 weeks,” GSK Chief Scientific Officer Tony Wood said. Rapt CEO Brian Wong called the deal “an attractive path forward” for the company’s programs. 2
A regulatory filing revealed GSK intends to kick off a cash tender offer—allowing shareholders to sell their stock directly—within 10 business days after signing. The deal hinges on investors tendering a majority of Rapt shares and securing U.S. antitrust approval via the Hart-Scott-Rodino process, the filing indicated. 3
Rapt shares hovered just under the offer price in late trading, creating a narrow spread that could widen sharply if the schedule falters.
Deal-arb desks will closely monitor the formal tender-offer documents and Rapt’s recommendation statement in the upcoming session, detailing the board’s stance and the procedures for shareholders.
The companies indicated they aim to close in the first quarter of 2026, with ozureprubart’s phase IIb trial — prestIgE — slated to deliver data in 2027.
If the deal goes through, GSK will secure global rights to ozureprubart everywhere except mainland China, Macau, Taiwan, and Hong Kong. It will also assume future milestone and royalty payments connected to Rapt’s partner, Shanghai Jeyou Pharmaceutical.
Tender offers aren’t foolproof. Regulators might drag out their reviews, shareholders could reject the offer, or a competing bidder might emerge — any of these would leave the stock tied to trial-readout calculations rather than a guaranteed cash payout.
The competitive bar is rising. Ozureprubart would enter a market where Genentech’s Xolair already targets a similar IgE pathway, while Novartis is testing remibrutinib for food allergy.
Investors are now focused on when the tender offer will kick off and the antitrust review period will begin. The next key date for the stock is the first-quarter close.
